TDLAS Verification via Fiber Bragg Grating Reference
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Solution Overview
Problem
Existing TDLAS systems lack a cost-effective, portable, and user-friendly method for verifying proper operation and ensuring reliable data generation, especially in industrial combustion environments where sealed spectroscopy cells are impractical due to elevated temperatures and pressure sensitivity.
Innovation Solution
A TDLAS sensing apparatus utilizing a fiber Bragg grating optical fiber that partially reflects a laser beam to create a stable, repeatable transmission spectrum mimicking an absorption dip at the select lasing frequency, allowing for continuous system verification and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sealed spectroscopy cell is used for TDLAS system verification, then measurement accuracy is improved, but the system becomes impractical for elevated temperature environments due to pressure sensitivity
Solution Approach 1:
The patent uses a fiber Bragg grating to create a reference transmission spectrum that copies the absorption dip pattern of the target gas species. This reference pattern serves as a stable, portable verification standard that mimics the fingerprint of real gas absorption without requiring actual gas samples or sealed cells, thereby maintaining measurement accuracy while eliminating environmental constraints.
Solution Approach 2:
The invention replaces the mechanical sealed spectroscopy cell system with an optical fiber-based reference system. The fiber Bragg grating creates a stable reference pattern optically, eliminating the need for physical containment structures that are sensitive to temperature and pressure changes.
2Adaptability or versatility
If a flowing cell system is used for calibration and verification, then environmental adaptability is improved, but device complexity and cost increase significantly
Solution Approach 1:
Instead of using a complex flowing cell system that requires gas supply infrastructure, temperature control, and flow management, the patent creates a simplified optical copy of the absorption spectrum using a fiber Bragg grating. This reference pattern captures the essential verification function without the accompanying complexity.
Solution Approach 2:
The invention extracts the essential verification function from the complex flowing cell system - creating a reference absorption pattern - and separates it from the unnecessary components (gas flow systems, temperature control, pressure regulation). The fiber Bragg grating provides only the critical reference pattern generation function.
3Reliability
If a flowing cell system is used for system verification, then reliability is improved, but portability and ease of operation deteriorate
Solution Approach 1:
The patent creates a portable reference absorption pattern copy using fiber Bragg grating technology that can be easily deployed in the field. This reference spectrum maintains reliability for verification purposes while being contained in a compact, transportable form factor that does not require complex infrastructure.
Solution Approach 2:
The invention segments the verification function from the complex flowing cell infrastructure, creating a standalone, self-contained reference system based on fiber optics that can be independently deployed without requiring gas supply systems or environmental control equipment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The fiber Bragg grating system provides a durable, lightweight, and cost-effective means to verify TDLAS system functionality by producing a consistent reference absorption pattern, enabling frequent comparisons and ensuring system health, even in harsh environments.
Implementation Method 1
A fiber Bragg grating (FBG) optical fiber is provided comprising at least one FBG formed in a core of the FBG optical fiber. The at least one FBG is configured to partially reflect a laser beam of a first select lasing frequency produced by the at least one diode laser
Implementation Method 2
Gas phase species that absorb some of the light cause a dip in the amount of transmitted light as the wavelength is scanned (an 'absorption dip')
Data Source
Figure 1~3
Figure 4
AI summary
Sensing of gas species characteristics within a process chamber includes selectively projecting a beam of a first select lasing frequency therethough. The beam is optically coupled to a detector to detect a process transmission spectrum having an absorption dip at a select lasing frequency caused by a gas species characteristic. The beam is selectively projected through a fiber Bragg grating which is formed in an optical fiber core to partially reflect at least a portion of the beam of the first select lasing frequency while passing a remainder of the beam. The remainder of the beam has an FBG transmission spectrum mimicking the absorption dip at or near the select lasing frequency caused by a gas species characteristic of interest. It is optically coupled the detector. Outputs of the detector are monitored to compare the FBG transmission spectrum to any process transmission spectrum produced in the process chamber.